Reds and yellows are higher elevations in this image.
NASA/JPL/Goddard

If it looks like an impact crater and walks like an impact crater, it may not actually be an impact crater. The Eden Patera basin on Mars has long been classified as an impact crater, but scientists are rethinking the designation based on a fresh look at images and topographic data.

One clue that points to a different origin is the lack of a raised rim around the basin, a feature usually found on impact craters. There are also signs of the ground collapsing, indicating long-ago activity below the surface. If the researchers are right, then this would be the first ancient supervolcano identified on the Red Planet.

"On Mars, young volcanoes have a very distinctive appearance that allows us to identify them. The long-standing question has been what ancient volcanoes on Mars look like. Perhaps they look like this one," says Mars researcher Joseph Michalski with the Planetary Science Institute and the Natural History Museum in London.

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When examined, Eden Patera shows a lot of similarity with Earth calderas that were formed by supervolcanoes. Calderas are huge depressions in the earth that form when the ground collapses into itself after a volcanic eruption. Supervolcano eruptions are thousands of times more powerful than a regular volcano and can spew enough ash and detritus to impact global weather patterns.

A paper published in Nature delves into the supervolcano identification and suggests that large amounts of magma spewed out from the site. This could lead to reevaluations of other craters in the same area, and could explain the presence of volcanic deposits elsewhere on the planet that have not yet been linked to specific volcanoes.

Jacob Bleacher, a volcano specialist at NASA's Goddard Space Flight Center, said, "If just a handful of volcanoes like these were once active, they could have had a major impact on the evolution of Mars."

About the author

Freelance writer Amanda C. Kooser covers gadgets and tech news with a twist for CNET's Crave blog. When not wallowing in weird gadgets and iPad apps for cats, she can be found tinkering with her 1956 DeSoto.
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